To restrict the slackening of a chain, there has been known a chain guide which forms a tunnel-like chain passage in a resilient body for allowing a chain to penetrate the chain passage and for bringing the chain into sliding contact with a bottom wall surface thereof. In such a chain guide, a structure is known in which longitudinal positions of respective front end portions of left and right side walls which constitute the chain passage are aligned, and a projecting guide rib which extends in the longitudinal direction is formed on the bottom wall surface with which the chain is brought into slide contact. See, for example, JP-A-8-207870.
With respect to an off-road vehicle which travels on rough terrain, at the time of performing cornering by inclining a vehicle body to a side on which a chain guide is provided or at the time of performing track traveling, the vehicle is operated while bringing a vehicle-body-outside side wall of the chain guide, into contact with a muddy road surface and there exists a possibility that mud or the like intrudes on the inside of the chain guide from the vicinity of a chain inlet of the chain guide. Since front end portions of left and right side walls of the chain guide are arranged at the same position, the mud or the like is not discharged at the inlet side and is discharged only from an outlet side.